The boss of Gatwick admitted on Tuesday the airport fell short in looking after the thousands of passengers stranded after power failures on Christmas Eve, but said that Met Office forecasts underestimated rainfall and flood warnings came too late.

EasyJet, the airline that operates most flights at Gatwick, blamed the airport for exacerbating passengers' troubles through a lack of communication and relying on a vastly under-resourced contingency plan.

Stewart Wingate, Gatwick's chief executive, told MPs on the transport select committee that "more could and should have been done for passengers" and reiterated his apologies, saying: "Our actions fell short."

He claimed risk assessments showed that the airport's north terminal was comparatively safe from flooding and that a £20m-investment on resilience had focused on the south terminal, which operated fully during the chaos, which saw many passengers waiting up to 12 hours before being told that their flights were cancelled.

Wingate, who was on leave in Newcastle on 24 December, said Gatwick had been making preparations for extreme winds but a warning that the nearby river Mole was set to flood came through only at 4.15am, half an hour before it broke its banks, as 68mm (2.7in) of rain fell overnight.

Two out of six switch rooms, which feed the electrical power source to parts of the airport, were flooded and put out of action.

At an emergency meeting the airport and airlines decided to try to switch flights to the south terminal to get passengers away for Christmas. Wingate said they made the "unprecedented switch ... with the best of intentions" but admitted, "it was a step too far".

While around a third of the north terminal flights departed, many more were eventually cancelled after customers had been subjected to long waits. Wingate said choosing whether to cancel early or risk trying to get passengers away was a very difficult decision.

He added: "On this occasion our actions and those of our airline partners fell short. At times like this passenger information and comfort must be a priority." He gave an undertaking that Gatwick would invest further to prevent a recurrence of scenes that eventually saw police advise airline staff to vacate areas of the airport as passengers' anger grew.

EasyJet representatives however accused Gatwick of failing to respond adequately to the situation. Jason Holt, the airline's head at Gatwick, said he arrived at the scene before senior airport staff. He told the committee: "What I was confronted with was something of biblical proportions... I had to stand on a table to be seen over thousands of customers and quieten them.

"In that process I didn't see many blue lanyards, I didn't see many Gatwick people. I saw a lot of distressed people who were looking at Christmas Eve with a very difficult day ahead of them. We had no screens, no electricity, no IT, no loudhailers, no information unless we went ferreting for it."

The airline said it concurred with Gatwick's plan to transfer passengers to the fully functioning south terminal before it was told how few buses were available. According to Peter Duffy, EasyJet's customer director, only at a delayed 1pm meeting did Gatwick admit it only had four buses – at which point it cancelled 57% of its flights. "We had 11,000 passengers an hour and buses to move around 500 from the north to south terminal … If we'd had that information up front at 7.30 we'd have made that decision a lot quicker."

Duffy said the disruption had already cost EasyJet around £2m in compensation for passengers including hotels, meals and rebooked flights.

Wingate however pointed to additional factors such as the closure of the M23 due to flooding, and the loss of rail services and power. "We shouldn't lose sight that this was an enormous event that was much bigger than Gatwick airport."

He said what while the systems had worked fine for decades, "We now have to take it to another level and invest millions for added resilience – there is no question of that, we will do it."

Gatwick has said all customers whose flights were cancelled on Christmas Eve will be given £100 worth of shopping vouchers as a goodwill gesture. The airport has launched its own inquiry, although MP Graham Stringer questioned whether David McMillan, the non-executive director, conducting the review, could be regarded as independent as he was primarily responsible to shareholders. A report is due in February.

Wingate said of the events: "Clearly it will have had an impact on our reputation. Hopefully we will able to regain the trust of our passengers in 2014."